📊 Phase 3 Delivers Blockbuster Results
The UK's Autonomy Institute and 4 Day Week Global released Phase 3 trial results on May 8, 2026, covering 92 companies and 4,800 employees across 14 sectors — the largest four-day workweek experiment ever conducted. Participating companies reduced working hours to 32 per week (typically four eight-hour days) with no reduction in pay, for a six-month trial period from October 2025 through March 2026.
The results were the strongest yet across all three UK trial phases: company revenue increased 8.2% year-over-year versus 3.1% for a matched control group of non-participating firms; sick days fell 57% (from 3.7 to 1.6 per employee per year); and employee turnover dropped 24%.
Employee well-being metrics showed even more dramatic improvements. Burnout scores, measured using the validated Maslach Burnout Inventory, improved 41%. Self-reported life satisfaction, measured on the OECD 0-10 scale, rose from 6.8 to 7.9.
Critically, 94% of participating companies — 86 out of 92 — stated they would continue the four-day week beyond the trial period, with 68% calling the change "a permanent transformation." Six companies reported reverting to five-day weeks, primarily citing client expectations in industries requiring daily availability, such as legal services and public accounting during tax season.
✨ Who Benefits Most
The largest productivity improvements were concentrated in marketing and advertising (14% revenue growth), technology and IT services (12%), professional services and consulting (11%), and nonprofit organizations (10%). Sectors requiring continuous physical operations — manufacturing, hospitality, retail — showed positive but smaller effects (2-4% revenue growth), largely achieving the reduction through shift redesign rather than straightforward day elimination.
Manufacturing firms reported that implementing four-day weeks required significant upfront investment in workflow automation, lean methodology training, and shift scheduling software. However, 76% of participating manufacturers still elected to continue, citing recruitment advantages in tight labor markets.
The trial's policy implications are significant. The UK Labour Party included a "right to request a four-day week" in its 2024 manifesto, and Business Secretary Jonathan Reynolds said the Phase 3 results "build a compelling parliamentary case." Similar legislation is advancing in Portugal, Spain, and Iceland. In the private sector, Kickstarter, Bolt, and Buffer have all made four-day weeks permanent, while Unilever's UK office completed its own successful 18-month pilot in March 2026.